The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Conventional internal combustion engine systems disable cylinder fueling when a torque demand of the engine is at or below zero. This control feature of the engine system is sometimes referred to as deceleration fuel cut-off (DFCO). DFCO provides the engine system with opportunities to cool one or more catalytic converters of the system and opportunities to reduce fuel consumption during the drive cycle.
Active fuel management engines deactivate one or more cylinders under specific low load operating conditions. For example, an eight cylinder engine can be operated using four cylinders to improve fuel economy by reducing pumping losses. Operation using all of the engine cylinders is referred to as an “activated” mode. Conversely, operation using less than all of the cylinders of the engine (i.e. one or more cylinders are not active) is referred to as a “deactivated” mode.
In the deactivated mode, fuel not delivered to selected cylinders. As a result, there is less drive torque available to drive the vehicle driveline and accessories (e.g., alternator, coolant pump, A/C compressor). However, engine efficiency is increased as a result of decreased air pumping losses due to the deactivated cylinders not taking in and compressing fresh intake air.
The opportunity to take advantage of the potential benefits of cutting off fuel to a cylinder for either DFCO or AFM is reduced by drivability concerns associated with transitioning into and out of this zero fueling mode.